http://media3.washingtonpost.com/wp-...0070205373.jpgWhen Apple chief executive Steve Jobs unveiled the iPhone 4 on June 7, he held the device in his left hand at times. Some users claim the smartphone loses signal strength if it is held in the left hand. (Paul Sakuma/associated Press)

The iPhone's software is "totally wrong" at reporting the strength of AT&T's wireless signals, Apple said in an apology to customers posted on its Web site Friday.

The computer and gadget company's "Letter from Apple Regarding iPhone 4" addressed complaints raised by a handful of users that its new iPhone 4 smartphone can lose signal strength if held in a user's left hand.

But while those complaints alleged a flaw in the iPhone's construction -- specifically, a gap between two antennas wrapped around its exterior that could be bridged by a finger placed in the wrong spot -- Apple chalked it up a programming error made long ago.

"Upon investigation, we were stunned to find that the formula we use to calculate how many bars of signal strength to display is totally wrong," Apple's letter read. "Our formula, in many instances, mistakenly displays 2 more bars than it should for a given signal strength."

Apple will ship a software update for the iPhone 4, and its earlier iPhone 3G and 3GS, that will display accurate signal strengths "within a few weeks," the note said.

The Cupertino, Calif., company's account, however, did not square with the experiences of some iPhone 4 users who complained that their new devices not only showed a weaker signal but also dropped calls.

A detailed radio-frequency analysis at the AnandTech site concluded that the iPhone 4's design caused it to lose more signal than other phones -- including Apple's older iPhone 3GS and Google's Nexus One -- when grasped in the same way. (That tech-news site's research also found that when held otherwise, the iPhone 4 provided much better reception than the 3GS.)

An Apple publicist did not respond to an e-mail and a voicemail message requesting comment Friday afternoon.

Three industry analysts did not predict any long-term issues for Apple, which reported selling 1.7 million iPhone 4s in the first three days after its June 24 debut.

"It remains to be seen whether new customers looking to switch to the iPhone might pause because of this," said Rajesh Ghai, an analyst at ThinkEquity. He said he thought it was only a small possibility and suggested that many people have iPhones for the 225,000-plus applications available for them -- and that consumers have grown accustomed to reception problems.

Coverage issues with AT&T, the only service option for the iPhone in the United States, don't seem to have slowed sales of Apple's smartphones, although customers can now choose from more devices with Web access and a selection of add-on applications comparable to the iPhones.

Smartphones running Google's Android software have become the main alternative to the iPhone. In May, the NPD Group reported that sales of Android devices sped past those of iPhones in the first quarter of 2010.

Other issues have beset Apple's mobile products lately. A flaw in AT&T's online-account system exposed the e-mail addresses of users of the 3G version of Apple's iPad, and neither Apple nor AT&T could keep up with pre-orders for the iPhone 4 before its retail debut.

"I don't think this announcement will put a dent in the line" for iPhones, said Carl Howe, director of consumer research at the Yankee Group. "It's causing people to question it, but people are buying them as fast as they can make them."

The damage here may instead fall on the iPhone's image of precision-engineered excellence. "It's negative for the brand," said Andy Hargreaves, an analyst at Pacific Crest Securities. "Does it mean they'll sell fewer iPhones? Probably not."